The present invention relates to a single-disc refiner for refining lignocellulosic material for paper and board manufacturing, comprising a stationary refining element and an opposed rotatable refining element, the stationary and rotatable refining elements each comprising at least one radially inner blade element providing an inner refining surface area of the refining element and at least one radially outer blade element providing an outer refining surface area of the refining element, the inner refining surface area and the outer refining surface area of each refining element together providing a refining surface of the refining element.
The present invention also relates to a blade element for a rotatable disc-like refining element of a refiner, the blade element being intended to provide at least part of a refining surface of the rotatable disc-like refining element and comprising an inner edge to be directed toward the center of the refining element and an outer edge to be directed toward the outermost edge of the refining element and a refining surface provided with blade bars and blade grooves therebetween.
Flat disc refiners for refining fibrous material for manufacturing paper and board typically comprise at least two opposite disc-like refining elements, at least one of which is rotating. A refining gap is provided between the two opposite elements. In so-called DD or double-disc refiners, both refining elements rotate in opposite directions, whereas in SD or single-disc refiners only one refining element rotates. A so-called Twin refiner is also a single-disc refiner comprising three refining elements, one of which is a rotatable element sandwiched between two stationary elements, whereby two refining gaps are provided.
Single-disc high-consistency refiners for wood chips and fibres comprise a stationary disc-like refining element and an opposed rotatable disc-like refining element, and have a blade gap or a refining gap therebetween, a suspension of water and wood chips to be refined being fed into the blade gap. In most single-disc high-consistency refiners the stationary and rotatable refining elements comprise an annular inner refining surface area and an annular outer refining surface area composed of one or more blade elements, whereby the inner refining surface area and the outer refining surface area of each refining element together provide a complete refining surface of the refining element.
Single-disc high-consistency wood chip refiners have a simple structure and operation. However, single-disc refiners typically operate with an undesirable high energy consumption and a low production capacity.
One example of single-disc refiners is disclosed in WO publication 95/25199.